The ornamental design for a displayscreen or portion thereof with icon, as shown and described.
FIG. 1 is a front view of a display screen or portion thereof with icon, showing our new design; and,
FIG. 2 is a front view of a display screen or portion thereof with icon of FIG. 1, in which a mobile terminal in broken line is provided to illustrate an example environment.
The broken lines showing a display screen or portion thereof form no part of the claimed design.